1. Field of the Invention
The present invention relates to a method for reducing the crystal defects in a SIMOX (Separation by IMplanted OXygen) wafer and to the SIMOX wafer and, more particularly, to a technique for reducing crystal defects present in a silicon layer underneath a buried oxide film of the SIMOX wafer.
2. Description of the Related Art
Conventionally, as one of methods for manufacturing an SOI (Silicon On Insulator) wafer, a SIMOX method has been known, in which oxygen ions are implanted from at least one of the surfaces of a silicon wafer, and then a high-temperature heat treatment is performed, thereby forming a buried oxide film (hereinafter referred to as a BOX (Buried Oxide) layer) by the implanted oxygen ions. The SIMOX wafer thus manufactured is generally shipped to a device manufacturer with a surface oxide film removed. A surface SOI layer and a BOX layer thereunder are utilized in a device manufacturing process.
Incidentally, it has been reported in recent years that, in a high-temperature heat treatment process of a SIMOX wafer manufacturing step, a multitude of crystal defects, i.e., vacancy-type stacking faults (SF) are left behind within a silicon layer underneath a BOX layer when an oxygen precipitate within the wafer vanishes. For example, refer to J. Jablonski and other two, “LETTERING LAYER FORMATION IN LOW-DOSE SIMOX WAFERS,” Proceedings 1995 IEEE International SOI Conference, October 1995, pp. 34-35.
In this regard, the silicon layer (silicon substrate) underneath the BOX layer has hardly been utilized conventionally in a device manufacturing process. Therefore, no measures have been taken against stacking faults remaining in the silicon layer.